Termite Season in Texas: When Swarms Happen and What to Watch For

Subterranean termites swarm in spring, generally March through May in Central Texas. The swarm is the colony's reproductive event: winged termites (called alates or swarmers) emerge to mate and establish new colonies. Swarming typically happens in the morning on warm, humid days following rain. The swarmers are poor fliers and drop quickly, losing their wings and pairing off to find a nesting site.

The swarm itself lasts 30 to 40 minutes and is easy to miss. What homeowners typically find afterward are the shed wings: small, equal-length wings piled on window sills, near door frames, or on exterior surfaces where the swarm emerged from the soil or wood nearby.

Eastern subterranean termites (Reticulitermes flavipes) are the most common species in San Antonio and the one responsible for most residential structural damage in Central Texas. They live in the soil and tunnel upward into wood, keeping their galleries moist by maintaining contact with the ground or moisture sources.

Formosan subterranean termites, a more aggressive invasive species, are present in parts of Texas including San Antonio. Formosan colonies grow much larger than native subterranean termites and can damage structures significantly faster. Formosan termites swarm at dusk and at night rather than midday, which helps distinguish them.

Drywood termites, which do not require soil contact, are present in South Texas but are less common in the San Antonio area than subterranean species. They swarm in late summer and fall.

The swarm is the most visible sign, but it is far from the only one. Mud tubes are the daily evidence of subterranean termite activity. These are pencil-width tunnels of mud and termite secretions that run along foundation walls, piers, in crawlspaces, along plumbing, and up into wood framing. They protect workers traveling from the soil to their food source. Mud tubes that are active contain live termites; empty tubes may be abandoned but are still worth investigating.

Wood that sounds hollow when tapped, paint bubbling over wood surfaces without a clear moisture source, floors that feel soft or springy in areas where they did not before, and door frames that have shifted or stuck are all potential signs of internal termite damage. The challenge with subterranean termites is that they eat from the inside out, so damage can progress considerably before anything looks wrong from the outside.

The two main approaches for subterranean termites are liquid soil treatments (termiticide barriers applied around the foundation) and baiting systems (monitoring stations placed in the soil around the property that deliver bait to colonies over time).

Liquid treatments create a chemical barrier in the soil that termites crossing it pick up and carry back to the colony. When done correctly with a thorough product application, these treatments provide durable protection. Baiting systems work more slowly but do not require drilling into the foundation and can eliminate colonies at the source rather than just blocking entry.

Treatment choice depends on construction type, the severity of the infestation, and whether an active infestation needs to be cleared or whether the goal is prevention. A professional termite inspection establishes which conditions are present before any treatment recommendation is made.

Subterranean termites need moisture and wood. Reducing both limits their access. Keep firewood, lumber, and wood debris away from the foundation. Ensure gutters direct water away from the structure and that the grade around the foundation slopes away from the house to prevent pooling. Fix any plumbing leaks in crawlspaces or under sinks promptly. Keep mulch several inches back from the foundation; deep mulch beds against foundation walls are a documented termite risk factor in South Texas.